1. Field of the Invention
The present invention relates to a display in which a visual point (seeing distance and seeing position) with respect to a display screen is specified in a narrow range, such as displays for displaying the pitcher's pitching motion installed in baseball or softball batting practice centers (so-called "batting centers") and displays for displaying the individual player's motion installed in tennis practicing centers (so-called "auto-tennis").
2. Description of the Conventional Art
In a baseball batting center, many pitching machines are employed to throw balls toward the batters' boxes about 15 to 20 m ahead thereof, and individual batters practice batting the thrown balls back while standing in the batters' boxes. However, in actual batting, the batter swings his bat by counting the ball pitching timing while watching the pitcher's pitching motion. Therefore, this system employing the pitching machines has a problem in that the batter has difficulty attempting to find the ball pitching timing.
To overcome this problem, the conventional batting centers have introduced a display 12 such as shown in FIG. 22. This display 12 is located in front of a batter 11 to display the pitching motion of a pitcher, and a ball is thrown by a pitching machine 13 at the same timing as the pitcher in the image throws the ball, so that the batter 11 can practice batting as if he were batting under actual conditions.
However, the batting centers are generally located outdoors where it is light, or is illuminated so that the ball can be seen with ease even if located indoors. Accordingly, to give a clear pitching motion image to the batter 11 who is as many as 20 m away from the display in such a place, a display screen having such a high luminance as to resist surrounding lightness is necessary, which in turn has imposed a problem that an expensive display 12 has to be used. In addition, displays 12 of adjacent batter's boxes are seen from the batter 11 in front of him or her in juxtaposition, and the pitching motions of these displays have therefore made it hard for the batter 11 to concentrate only on the image of the display 12 for his batter's box, which is another problem.
This problem can be temporarily overcome by arranging in front of the display 12 a grating-like shielding member or the like for blocking injection of external light. However, if a grating-like shielding member is arranged, the batter 11 finds it easy to see the image just as long as the visual point of the batter 11 stays right in front of the display 12, but if the relative positional relationship between the visual point and the display 12 is shifted up, down, left, and right to a large degree due to installation conditions, a ratio at which the visibility of an image is disturbed by the light-shielding member (image disturbing ratio) is increased, thus imposing the problem that the batter finds it hard to see the image.
In this case, leftward and rightward displacements of the visual point can be corrected with ease by turning the display 12 horizontally so that the display screen faces directly in front of the batter's box. However, for the correction of upward and downward displacements of the visual point, it is necessary to (1) make the display 12 installation level substantially as high as the ground level of the batter's box; (2) to install the display 12 so as to be inclined; or (3) to insert an angle adjusting spacer into the lower end of the display 12; and the like. However, case (1) entails a large construction work and cost, and cases (2) and (3) require not only cumbersome and laborious work in making fine angle adjustments due to the display 12 being large-sized and heavy, but also make it likely that the display 12 will fall down due to the center of gravity of the display 12 being one-sided.